1. Field of the Invention
The present invention relates to a three-dimensional measurement apparatus and a three-dimensional measurement method for measuring the three-dimensional shape of an object to be measured by radiating and scanning the object with a laser beam and reading reflected light therefrom.
2. Description of the Related Art
One of the currently available methods for obtaining three-dimensional profile information of an object is an optical sectioning method. As shown in FIG. 7, slit light is projected to an object while scanning it, and reflected light therefrom is received by an image sensor of a camera. By measuring timings on which the reflected light is received per pixel, a distance from an imaging surface of the image sensor to an object to be measured is measured in accordance with the principle of triangulation (for example, refer to Japanese Patent Application Laid-Open Publication No. 2001-280926, Japanese Patent Application Laid-Open Publication No. 2001-108418).
Typically, in the above-mentioned optical sectioning method, a typical CCD image sensor is employed for receiving light. In this case, the frame rate is limited to about 30 fps. If it is desirable to maintain a certain degree of distance resolution, the scanning rate has to be slowed down, thus making it difficult to use for real-time measuring of a moving object.
In order to address the above point, a system that enables a high-speed measurement by improving an image sensor is disclosed in Japanese Patent Application No. 2001-287625 (Japanese Patent Application Laid-Open Publication No. 2003-169251, Published Date: Jun. 13, 2003).
In FIG. 6 of the above-mentioned Japanese Patent Application Laid-Open Publication No. 2003-169251, the principle of triangulation and the principle of three-dimensional measurement based on a laser slit light are described.
The above-mentioned system is designed for allowing each pixel to detect a passing timing of the slit light at a high speed by carrying out a differential calculation with a high frame rate inside the image sensor. In the above-mentioned system, it is possible to measure a distance image at 15 fps or 30 fps by means of carrying out the differential calculation by the image sensor at 3.3 kfps.